1. Field of the Invention
This invention concerns polyurea elastomers, useful in solventless spray coatings, and more particularly to polyurea elastomers made using polyamine/carbonyl adducts as chain extenders.
2. Description of Related Information
Polyurea elastomers have found widespread utility, including as coatings such as for spray applications. These materials have a desirable balance of properties including: light stability; fast cure; relative water insensitivity; solventless systems; excellent physical properties, including tensile strength, elongation and abrasion resistance; pigmentation capability; ease of application, such as using commercially available spray application equipment; and, since no catalyst is needed, consistent reactivity and long term storage stability. These and other well known properties are discussed in the literature, such as by D.J. Primeaux II, in "Spray Polyurea, Versatile High Performance Elastomer for the Polyurethane Industry", Proceedings of the SPI 32nd Annual Technical/Marketing Conference, pages 126-130, Oct. 1989; and by D.J. Primeaux II, in "Sprayed Polyurea Elastomers Offer Superior Performance", UTECH'90. pages 189-194, Apr. 1990.
Polyureas can be made by reacting amines with isocyanates. For example, U.S. Pat. No. 4,732,919 (Grigsby, Jr. et al.) discloses polyurea elastomer made from high molecular weight polyol or polyoxyalkylene polyamine, chain extender and quasi-prepolymer of polyoxyalkylene polyamine and aromatic isocyanate. Polyurea spray formulations based on aliphatic isocyanates and chain extenders are disclosed in U.S. patent application Ser. No. 07/402,296 filed Sep. 5, 1989 and in a publication by Texaco Chemical Company entitled "Technical Bulletin, Polyurea Spray Formulations Based on Aliphatic Isocyanates and Chain Extenders", 1990. Aliphatic polyurea elastomer, useful in instrument panels, made from aliphatic isocyanate, amine-terminated polyoxyalkylene polyol and amine-terminated aliphatic chain extender is disclosed in U.S. patent application Ser. No. 07/479,015 filed Feb. 9, 1990.
Some polyurea elastomers, however, can have undesirable curing properties, such as residual tackiness, limiting their utility. There is therefore a need for polyurea elastomers which have improved cure properties.